Dual Hydrogel Research Articles

Myelinated 3D neural culture platform as a physiological model of diabetic peripheral neuropathy

Event Abstract Back to Event Myelinated 3D neural culture platform as a physiological model of diabetic peripheral neuropathy Ashwin Sivakumar1, Reed Gioe1 and Michael Moore1, 2 1 Tulane University, Department of Biomedical Engineering, United States 2 Tulane University, Department of Neuroscience, United States Introduction: We present a microengineered 3D hydrogel platform for culture of myelinated embryonic peripheral neural tissue as shown in Figure 1. This novel in-vitro platform enables morphological and physiological metrics analogous to clinical nerve fiber density and nerve conduction tests. We demonstrate the feasibility of this model system for studying peripheral neuropathy caused by glucose-induced neurotoxicity, the most common form of neuropathy. Figure 1: Microengineered myelinated neural fiber tract 3D architecture resembling native peripheral nerve anatomy. Materials and Methods: Dorsal root ganglia (DRG) from embryonic day 15 rats were grown over a period of 4 weeks in a dual hydrogel system consisting of a methacrylated heparin gel in a polyethylene glycol micro-mold. The dual hydrogel system served to constrain the axon growth to be polarized with high density, fasciculation and myelination. The DRG’s were subject to a three-stage media regimen including ascorbic acid (AA) in the final stage to induce Schwann Cell myelination. The myelinated cultures were subjected to 60mM concentrations of the D-glucose in media over a period of 48 hours to simulate diabetic neuropathy. The control cultures were exposed to a 25mM D-glucose concentration. Electrophysiological field recordings were taken with and without the exposure of high glucose, and changes in the compound action potentials in the field recording were observed and compared to the control. Results and Discussion: Compound action potentials show little or no synaptic input, increased delay and decreased amplitude with higher glucose concentration exposure as shown in Figure 2. The higher glucose concentration is thought to trigger the sorbitol pathway and induce oxidative stress in the neurons of the DRG, leading to apoptosis and axonal degeneration. Figure 2: Average traces representing compound action potentials recorded with and without high glucose treatment. The change in amplitude and latency are also quantified as bar plots. (n=10, * = p<0.05 and ***=p<0.001) Conclusion: Microengineered myelinated neural fiber tracts have morphology, physiology and, toxicity response analogous to a peripheral nerve. The platform could be used as an in-vitro model for neuropathy studies and drug development. Funding provided by Tulane University

Bioorthogonal Radiopaque Hydrogel for Endoscopic Delivery and Universal Tissue Marking.

A novel dual marking hydrogel system is reported for radiological and laparoscopic localization of lesions. Bioorthogonally crosslinked hydrogel containing both tantalum and India ink can be rapidly formed inside the body after injecting precursors, and stably located for several days as a long-term biocompatible carrier for markers.

Influence ofMEOBiPAcontent on the properties of novel photoluminescent thermosensitive hydrogels

AbstractIn order to establish a dual functional hydrogel, a special monomer, methacryloyloxy‐ethylene‐oxy‐carbonyl bis[4‐(phenyl‐isopropyl)phenyl]amine (MEOBiPA), was prepared from bis[4‐(phenyl‐isopropyl)phenyl]‐4‐cyanophenyl amine and 2‐hydroxyethyl methacrylate. Subsequently, a series of thermosensitive hydrogels was obtained through copolymerization ofN‐isopropyl acrylamide (NIPAAm) withMEOBiPAbyUVirradiation (named theNMseries). The effect ofMEOBiPAcontent on the swelling behavior, mechanical properties and drug release behavior of the hydrogels was further investigated. Results showed that the swelling ratios of theNMcopolymeric hydrogels decreased from 4.73 to 1.74 g g−1when theMEOBiPAcontent in the hydrogel increased from 0.1 to 0.9 mol%. Both gel strength and crosslinking density of theNMhydrogels increased with increasingMEOBiPA. Conversely, the thermosensitive behavior ofNMhydrogels significantly decreased upon increase ofMEOBiPAcontent. Likewise, the caffeine release ratio also decreased from 70% to 25%. Notably, the intensity of photoluminescence increased with increasingMEOBiPAcontent in the hydrogels. Further, the corresponding copolymers of the hydrogels were prepared using free radical polymerization. TheUVabsorbance and photoluminescent behavior of theMEOBiPA,NIPAAm/MEOBiPAcopolymeric hydrogels and their corresponding copolymers in different polar solvents were also investigated. © 2015 Society of Chemical Industry

Dual Thermosensitive Hydrogels Assembled from the Conserved C-Terminal Domain of Spider Dragline Silk.

Stimuli-responsive hydrogels have great potentials in biomedical and biotechnological applications. Due to the advantages of precise control over molecular weight and being biodegradable, protein-based hydrogels and their applications have been extensively studied. However, protein hydrogels with dual thermosensitive properties are rarely reported. Here we present the first report of dual thermosensitive hydrogels assembled from the conserved C-terminal domain of spider dragline silk. First, we found that recombinant C-terminal domain of major ampullate spidroin 1 (MaSp1) of the spider Nephila clavipes formed hydrogels when cooled to approximately 2 °C or heated to 65 °C. The conformational changes and self-assembly of the recombinant protein were studied to understand the mechanism of the gelation processes using multiple methods. It was proposed that the gelation in the low-temperature regime was dominated by hydrogen bonding and hydrophobic interaction between folded protein molecules, whereas the gelation in the high-temperature regime was due to cross-linking of the exposed hydrophobic patches resulting from partial unfolding of the protein upon heating. More interestingly, genetic fusion of the C-terminal domain to a short repetitive region of N. clavipes MaSp1 resulted in a chimeric protein that formed a hydrogel with significantly improved mechanical properties at low temperatures between 2 and 10 °C. Furthermore, the formation of similar hydrogels was observed for the recombinant C-terminal domains of dragline silk of different spider species, thus demonstrating the conserved ability to form dual thermosensitive hydrogels. These findings may be useful in the design and construction of novel protein hydrogels with tunable multiple thermosensitivity for applications in the future.

Curcumin delivered through bovine serum albumin/polysaccharides multilayered microcapsules.

The aim of the paper is to obtain and characterize k-carrageenan-chitosan dual hydrogel multilayers shell BSA gel microcapsules, as a carrier for curcumin, and as a possible antitumoral agent in biological studies. We used the CaCO3 template to synthesize non-toxic CaCO3/BSA particles as microtemplates by coprecipitating a CaCl2 solution that contains dissolved BSA, with an equimolar Na2CO3 solution. The microcapsules shell is assembled through a layer-by-layer deposition technique of calcium cross-linked k-carrageenan hydrogel alternating with polyelectrolite complex hydrogel formed via electrostatic interactions between k-carrageenan and chitosan. After the removal of CaCO3 through Ca(2+) complexation with EDTA, and by a slightly treatment with HCl diluted solution, the BSA core is turned into a BSA gel through a thermal treatment. The BSA gel microcapsules were then loaded with curcumin, through a diffusion process from curcumin ethanolic solution. All the synthesized particles and microcapsules were stucturally characterized by: Fourier Transform Infrared Spectroscopy, UV-Vis Spectrometry, X-ray diffraction, thermal analysis, fluorescence spectroscopy, fluorescence optical microscopy, confocal laser scanning microscopy and scanning electron microscopy. The behavior of curcumin loaded microcapsules in media of different pH (SGF, SIF and PBS) was studied in order to reveal the kinetics and the release profile of curcumin. The invitro evaluation of the antitumoral activity of encapsulated curcumin microcapsules on HeLa cell line and the primary culture of mesenchymal stem cells is the main reason of the microcapsules synthesis as BSA-based vehicle meant to enhance the biodisponibility of curcumin, whose anti-tumor, anti-oxidant and anti-inflammatory properties are well known.

Synthesis and characterization of novel dual environment-responsive hydrogels of Hydroxyethyl methacrylate and Methyl cellulose

The current study describes the synthesis and characterization of dual environment-responsive semi-interpenetrating hydrogels of polyhydroxyethyl methacrylate (pHEMA) and methyl cellulose (MC). HEMA was polymerized using free radical polymerization technique. Different proportions of MC were incorporated within the pHEMA matrix to induce environment-sensitive property. The microstructures of the hydrogels were studied under bright field microscopy. The hydrogels were thoroughly characterized using XRD, FTIR, swelling, mechanical and electrical studies. The micrographs of the hydrogels suggested formation of biphasic system. At lower proportions of MC, the hydrogels were oil-in-water type of formulations. An increase in the MC content resulted in the formation of bicontinuous biphasic formulations. Mechanical analysis suggested viscoelastic solid nature of the hydrogels. An increase in the MC content resulted in the increase in the viscous component. The electrical studies suggested resistive dominant behavior of the hydrogels. Thermal studies suggested better moisture retention capacity of the MC containing hydrogels. The hydrogels were found to be biocompatible in nature.

Effect of montmorillonite on the rheological properties of dually crosslinked guar gum‐based hydrogels

ABSTRACTOne strategy to create chemical and physical cross‐links simultaneously is to introduce into the chemical network hydrogen bonding with clay nanofillers. Understanding the relaxation mechanisms of these systems is crucially important and has drawn the extensive interest of many scientists. In this work, the influence of different amounts of montmorillonite on the structural and rheological properties of guar gum hydrogels was investigated. Depending on the clay content, different nanostructures were identified by X‐ray diffraction (XRD) and their effect on the rheological properties of the dual hydrogels was studied. From stress and frequency sweep tests it emerged that all the samples exhibit a weak gel behavior and showed a maximum for G″ that can be ascribed to the breaking and reforming of transient physical crosslinks. This relaxation mode is more pronounced for the hydrogel for which a minimum in the swelling degree was observed. On the basis of these results, a model structure was proposed according to which the clay sheets act as effective multifunctional cross‐linkers. The more homogeneously dispersed are the clay platelets, the higher is the density of physical crosslinks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41373.

Biofabricated film with enzymatic and redox-capacitor functionalities to harvest and store electrons

Exciting opportunities in bioelectronics will be facilitated by materials that can bridge the chemical logic of biology and the digital logic of electronics. Here we report the fabrication of a dual functional hydrogel film that can harvest electrons from its chemical environment and store these electrons by switching the film's redox-state. The hydrogel scaffold was formed by the anodic deposition of the aminopolysaccharide chitosan. Electron-harvesting function was conferred by co-depositing the enzyme glucose dehydrogenase (GDH) with chitosan. GDH catalyzes the transfer of electrons from glucose to the soluble redox-shuttle NADP+. Electron-storage function was conferred by the redox-active food phenolic chlorogenic acid (CA) that was enzymatically grafted to the chitosan scaffold using tyrosinase. The grafted CA undergoes redox-cycling reactions with NADPH resulting in the net transfer of electrons to the film where they are stored in the reduced state of CA. The individual and dual functionalities of these films were demonstrated experimentally. There are three general conclusions from this proof-of-concept study. First, enzymatically-grafted catecholic moieties confer redox-capacitor function to the chitosan scaffold. Second, biological materials (i.e. chitosan and CA) and mechanisms (i.e. tyrosinase-mediated grafting) allow the reagentless fabrication of functional films that should be environmentally-friendly, safe and potentially even edible. Finally, the film's ability to mediate the transfer of electrons from a biological metabolite to an electrode suggests an approach to bridge the chemical logic of biology with the digital logic of electronics.

Structural and molecular micropatterning of dual hydrogel constructs for neural growth models using photochemical strategies

Chemotactic and haptotactic cues guide neurite growth toward appropriate targets by eliciting attractive or repulsive responses from the neurite growth cones. Here we present an integrated system allowing both structural and molecular micropatterning in dual hydrogel 3D tissue culture constructs for directing in vitro neuronal growth via structural, immobilized, and soluble guidance cues. These tissue culture constructs were fabricated into specifiable geometries using UV light reflected from a digital micromirror device acting as a dynamic photomask, resulting in dual hydrogel constructs consisting of a cell growth-restrictive polyethylene glycol (PEG) boundary with a cell growth-permissive interior of photolabile α-carboxy-2-nitrobenzyl cysteine agarose (CNBC-A). This CNBC-A was irradiated in discrete areas and subsequently tagged with maleimide-conjugated biomolecules. Fluorescent microscopy showed biomolecule binding only at the sites of irradiation in CNBC-A, and confocal microscopy confirmed 3D binding through the depth of the construct. Neurite outgrowth studies showed contained growth throughout CNBC-A. The diffusion rate of soluble fluorescein-bovine serum albumin through the dual hydrogel construct was controlled by PEG concentration and the distance between the protein source and the agarose interior; the timescale for a transient protein gradient changed with these parameters. These findings suggest the dual hydrogel system is a useful platform for manipulating a 3D in vitro microenvironment with patterned structural and molecular guidance cues for modeling neural growth and guidance.

Quantitatively controlled in situ formation of hydrogel membranes in microchannels for generation of stable chemical gradients

The in situ formation of membranes in microfluidic channels has been given attention because of their great potential in the separation of components, cell culture support for tissue engineering, and molecular transport for generation of chemical gradients. Among these, the porous membranes in microchannels are vigorously applied to generate stable chemical gradients for chemotaxis-dependent cell migration assays. Previous work on the in situ fabrication of membranes for generating the chemical gradient, however, has had several disadvantages, such as fluid leaking, uncontrollable membrane thickness, need of extra equipment, and difficulty in realizing stable interfacial layers. In this paper, we report a novel technique for the in situ formation of membranes within microchannels using enzymatically crosslinkable hydrogels and microfluidic techniques. The thickness of the membrane can be controlled quantitatively by adjusting the crosslinking reaction time and velocity of the microfluidics. By using these techniques, parallel dual hydrogel membranes were prepared within microchannels and these were used for the generation of stable concentration gradients. Moreover, the migration of Salmonella typhimurium was monitored to validate the efficacy of the chemical gradients. These results suggest that our in situ membrane system can be used as a simple platform to understand many cellular activities, including cell adhesion and migration directed by chemotaxis or complex diffusions from biological fluids in three-dimensional microstructures.

Facile micropatterning of dual hydrogel systems for 3D models of neurite outgrowth

Understanding how microenvironmental factors influence neurite growth is important to inform studies in nerve regeneration, plasticity, development, and neurophysiology. In vitro models attempting to more accurately mimic the physiological environment by provision of a 3D growth matrix may provide useful foundations. Some limitations of thick 3D culture models include hampered solute transport, less-robust neurite growth than on 2D substrates, and difficulty in achieving spatial control of growth. To this end, we describe a 3D dual hydrogel model for embryonic rat day 15 dorsal root ganglion tissue explant growth using a digital micromirror device for dynamic mask projection photolithography. The photolithography method developed allowed simple, reproducible, one-step fabrication of thick hydrogel constructs on a variety of substrates, including permeable cell culture inserts. The relationships between projected mask size, crosslinked hydrogel resolution, and gel thickness were characterized, and resolution was found generally to decrease with increasing gel thickness. Cell viability in thick (481 μm) hydrogel constructs was significantly greater on permeable supports than glass, suggesting transport limitations were somewhat alleviated. The observed neurite growth was abundant and occurred in a spatially controlled manner throughout the 3D environment, a crucial step in the quest for a more effective biomimetic model of neurite outgrowth.

Thermo- and pH-sensitive behavior of hydrogels based on oligo (ethylene glycol) methacrylates and acrylic acid

Novel dual stimuli-responsive hydrogels were prepared by free-radical polymerization of 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo (ethylene glycol) methacrylate (OEGMA), as thermosensitive monomers, and acrylic acid (AAc), as a pH-sensitive monomer. Due to the thermosensitive monomers introduced in the macromolecular network, the synthesized materials possessed tunable thermal behavior. In addition, as well as by introducing in the polymerization feed pH-sensitive monomer AAc, the equilibrium swelling properties of the hydrogels can be tuned by three comonomers. Moreover, the de-swelling kinetics was studied by changing temperature and/or pH, and they could be well described with a first-order kinetics equation. Especially, the faster shrinking rates of hydrogels were observed when the simultaneous temperature and pH stimuli changed from pH 8/18 to pH 2/55 °C because of the cooperative thermo-/pH responses. The prepared dual temperature-/pH-sensitive PMOA hydrogels as a new material candidate may provide significant valuable information for various potential applications.

Fabrication of Micropatterned Hydrogels for Neural Culture Systems using Dynamic Mask Projection Photolithography

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the need for 3D environments to represent in vitro experiments which better mimic in vivo qualities 1-3. Studies in fields such as cancer research 4, neural engineering 5, cardiac physiology 6, and cell-matrix interaction7,8have shown cell behavior differs substantially between traditional monolayer cultures and 3D constructs.Hydrogels are used as 3D environments because of their variety, versatility and ability to tailor molecular composition through functionalization 9-12. Numerous techniques exist for creation of constructs as cell-supportive matrices, including electrospinning13, elastomer stamps14, inkjet printing15, additive photopatterning16, static photomask projection-lithography17, and dynamic mask microstereolithography18. Unfortunately, these methods involve multiple production steps and/or equipment not readily adaptable to conventional cell and tissue culture methods. The technique employed in this protocol adapts the latter two methods, using a digital micromirror device (DMD) to create dynamic photomasks for crosslinking geometrically specific poly-(ethylene glycol) (PEG) hydrogels, induced through UV initiated free radical polymerization. The resulting "2.5D" structures provide a constrained 3D environment for neural growth. We employ a dual-hydrogel approach, where PEG serves as a cell-restrictive region supplying structure to an otherwise shapeless but cell-permissive self-assembling gel made from either Puramatrix or agarose. The process is a quick simple one step fabrication which is highly reproducible and easily adapted for use with conventional cell culture methods and substrates.Whole tissue explants, such as embryonic dorsal root ganglia (DRG), can be incorporated into the dual hydrogel constructs for experimental assays such as neurite outgrowth. Additionally, dissociated cells can be encapsulated in the photocrosslinkable or self polymerizing hydrogel, or selectively adhered to the permeable support membrane using cell-restrictive photopatterning. Using the DMD, we created hydrogel constructs up to ~1mm thick, but thin film (<200 μm) PEG structures were limited by oxygen quenching of the free radical polymerization reaction. We subsequently developed a technique utilizing a layer of oil above the polymerization liquid which allowed thin PEG structure polymerization.In this protocol, we describe the expeditious creation of 3D hydrogel systems for production of microfabricated neural cell and tissue cultures. The dual hydrogel constructs demonstrated herein represent versatile in vitro models that may prove useful for studies in neuroscience involving cell survival, migration, and/or neurite growth and guidance. Moreover, as the protocol can work for many types of hydrogels and cells, the potential applications are both varied and vast.

Fabrication of Micropatterned Hydrogels for Neural Culture Systems using Dynamic Mask Projection Photolithography

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the need for 3D environments to represent in vitro experiments which better mimic in vivo qualities 1-3. Studies in fields such as cancer research 4, neural engineering 5, cardiac physiology 6, and cell-matrix interaction7,8have shown cell behavior differs substantially between traditional monolayer cultures and 3D constructs. Hydrogels are used as 3D environments because of their variety, versatility and ability to tailor molecular composition through functionalization 9-12. Numerous techniques exist for creation of constructs as cell-supportive matrices, including electrospinning13, elastomer stamps14, inkjet printing15, additive photopatterning16, static photomask projection-lithography17, and dynamic mask microstereolithography18. Unfortunately, these methods involve multiple production steps and/or equipment not readily adaptable to conventional cell and tissue culture methods. The technique employed in this protocol adapts the latter two methods, using a digital micromirror device (DMD) to create dynamic photomasks for crosslinking geometrically specific poly-(ethylene glycol) (PEG) hydrogels, induced through UV initiated free radical polymerization. The resulting "2.5D" structures provide a constrained 3D environment for neural growth. We employ a dual-hydrogel approach, where PEG serves as a cell-restrictive region supplying structure to an otherwise shapeless but cell-permissive self-assembling gel made from either Puramatrix or agarose. The process is a quick simple one step fabrication which is highly reproducible and easily adapted for use with conventional cell culture methods and substrates. Whole tissue explants, such as embryonic dorsal root ganglia (DRG), can be incorporated into the dual hydrogel constructs for experimental assays such as neurite outgrowth. Additionally, dissociated cells can be encapsulated in the photocrosslinkable or self polymerizing hydrogel, or selectively adhered to the permeable support membrane using cell-restrictive photopatterning. Using the DMD, we created hydrogel constructs up to ~1mm thick, but thin film (<200 μm) PEG structures were limited by oxygen quenching of the free radical polymerization reaction. We subsequently developed a technique utilizing a layer of oil above the polymerization liquid which allowed thin PEG structure polymerization. In this protocol, we describe the expeditious creation of 3D hydrogel systems for production of microfabricated neural cell and tissue cultures. The dual hydrogel constructs demonstrated herein represent versatile in vitro models that may prove useful for studies in neuroscience involving cell survival, migration, and/or neurite growth and guidance. Moreover, as the protocol can work for many types of hydrogels and cells, the potential applications are both varied and vast.

Hydrogels Based on Dual Curable Chitosan-graft-Polyethylene Glycol-graft-Methacrylate: Application to Layer-by-Layer Cell Encapsulation

Ultraviolet (UV) photo-cross-linkable hydrogels have been commonly used for three-dimensional (3D) encapsulation of cells. Previous UV cross-linkable hydrogels have employed one-shot hardening of mixtures of hydrogels and cells. Here we propose an alternative method of making hydrogel-encapsulated cell constructs through layer by layer (LBL) buildup of alternating layers of cells and hydrogel. The LBL method potentially permits better spatial control of different cell types and control of cell orientation. Each hydrogel layer must be hardened before deposition of the next layer of cells. A UV-curable gel precursor that can also be gelled at physiological temperature is desirable to avoid repeated UV exposure of cells after deposition of each successive hydrogel layer. We designed, synthesized, and applied such a precursor, dual-curable-both thermoresponsive and UV-curable-chitosan-graft-polyethylene glycol-graft-methacrylate (CEGx-MA) copolymer (x is the PEG molecular weight in Daltons). We found that CEG350-MA copolymer solutions (5 wt % polymer) formed physical gels at approximately 37 degrees C and could be further photopolymerized to form thermally stable dual-cured hydrogels. This material was applied to the creation of a two-layer LBL smooth muscle cell (SMC)/hydrogel construct using temperature elevation to approximately 37 degrees C to gel each hydrogel layer. The physically gelled two-layered hydrogel/cell construct was finally exposed to a single UV shot to improve its mechanical properties and render it thermally stable. CEG350-MA solution and gel are nontoxic to SMCs. Cells remained mostly viable when they were encapsulated inside both physically gelled and dual-cured CEG350-MA and suffered little damage from the single brief UV exposure. The combination of LBL tissue engineering with a dual curable hydrogel precursor such as CEG350-MA permits the buildup of viable thick and complex tissues in a stable, biocompatible, and biodegradable matrix.

Dual thermo- and pH-sensitive poly( N-isopropylacrylamide-co-acrylic acid) hydrogels with rapid response behaviors

Novel dual temperature- and pH-sensitive comb-type grafted poly( N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)) hydrogels were successfully prepared by grafting PNIPAM chains with freely mobile ends onto the backbone of a cross-linked P(NIPAM-co-AAc) network. The prepared comb-type grafted P(NIPAM-co-AAc) hydrogels exhibited a more rapid deswelling rate than normal-type P(NIPAM-co-AAc) hydrogels in ultrapure water in response to abrupt changes from 25 °C to 60 °C. The same was true in buffer solution with a pH jump from 7.4 to 2.0 at 25 °C. Unexpectedly, the comb-type grafted P(NIPAM-co-AAc) hydrogels showed abnormal shrinkage behaviors in a buffer solution when the temperature increased from 25 °C to 60 °C with a pH value fixed at 7.4 or 2.0. In a buffer solution of pH 7.4, when the environmental temperature jumped from 25 °C to 60 °C, the grafted comb-type hydrogels shrank slower than the normal-type hydrogels, while at pH 2.0, the gels shrank faster than the normal-type gels in the beginning, which was followed by a slower shrinking. Interestingly, the much quicker shrinkage of the comb-type grafted P(NIPAM-co-AAc) hydrogels was observed because of the cooperative thermo-/pH-responses when the simultaneous temperature and pH stimuli met from pH 7.4/25 °C to pH 2.0/60 °C. The results of this study provide valuable information regarding the development of dual stimuli-sensitive hydrogels with fast responsiveness.

Morphology of poly(methacrylic acid)/poly(N-isopropyl acrylamide) interpenetrating polymeric networks

The morphology of interpenetrating polymeric networks (IPNs) composed of the temperature-sensitive poly(N-isopropyl acrylamide) (PNIPAAm) and the pH-sensitive poly(methacrylic acid) (PMAA) were investigated by scanning electron microscopy (SEM). The IPN hydrogels were prepared by a sequential UV polymerization method. SEM studies were conducted on IPN hydrogel samples dried by different methods, and the influence on the IPN structure was discussed. The environmental conditions induced morphological changes for these dual sensitive IPN hydrogels which were studied by cryogenic SEM, when the gels were analyzed in their wet state. The results showed that the porous size in the IPN was strongly influenced by the environmental pH and temperature. Decrease in pH and increase in temperature resulted in significant pore size decrease for the swollen IPNs hydrogels.